On a handgun, laser.
Shotgun, light.
Personally, I don't differentiate that much between long guns and handguns (in a home defense scenario). In my opinion, we all must have a light source of some kind in order to identify potential targets, possibly in complete darkness. A weapon-mounted light can serve this purpose for both long guns and handguns, operated in both cases by the support hand. This takes some training to avoid pointing the muzzle of either class of firearm directly at potential targets before they are identified and minimize the risk of accidentally shooting the wrong person.
As for the differences, handguns allow you to use a flashlight in the support hand instead, allowing you to direct the beam independently of the muzzle, which is useful, but the tradeoffs are that you may have to put the flashlight down or in your pocket in order to use your support hand for other purposes, and you won't have the most solid two-handed grip on your gun. I would recommend having both types of light available, if possible (note that weapon-mounted lights are bulky to carry, which is a non-issue for home defense), using one as the primary according to whatever you are more comfortable with, and keeping the other as a backup (I don't trust batteries).
Regarding lasers, they're useful for various aspects of training, but are unnecessary for those who are proficient with iron sights (except perhaps for some odd cases where you can't use the sights). I wouldn't bother with actually using one for defensive purposes unless I were currently under-proficient with iron sights for any reason (e.g. lack of training, various physiological issues), in which case anything that would make me a more effective shooter is justified, including lasers. If you do choose to use a laser, then be aware that they barely work in the daytime (useless in sunlight), and that you should keep developing your skill with iron sights and point-shooting (like I said, I don't trust batteries).
Finally, night sights are not absolutely necessary for everybody, but they can help under some conditions, and aside from cost there is really no reason not to recommend them.
In order of importance:
1) Light source - A usefully bright, directed light that helps you reliably identify people is a must, whether it is mounted on your weapon or held in your hand (or both).
2) Night sights - If you don't mind paying for them, they can come in handy at times, and really have no tradeoffs unless you happen to shoot better with all-black sights.
3) Laser - Use one as a crutch if you must (anything to improve your odds of survival, if in fact it would), but try to wean yourself off it by training with the iron sights (under all lighting conditions).